Interference of Implicit Causality in Relative Clause Processing

Differences in the processing of subject and object relative clauses have been explained by a combination of syntactic, semantic, and pragmatic factors, such as a general subject advantage based on syntactic constraints, effects of animacy, and the discourse status of relative clause internal subjects. In this paper, we will focus on a factor related to verb meaning, the implicit causality of the verb, which biases the principal causer of the event described by the verb. Depending on whether the bias is on the subject or the object, implicit causality can conflict with the foregrounded antecedent of the relative clause, leading to increased difficulty in comprehension. We tested this hypothesis by manipulating implicit causality in subject and object relative clauses. We used both offline (acceptability judgment task) and online (self-paced reading task) methods to observe at which stage of processing implicit causality influences comprehension. Our findings from acceptability judgments showed that object relative clauses with subject-biased verbs were the least acceptable and the least understood. Conversely, object relative clauses with object-biased verbs were as acceptable and easy to understand as subject relative clauses in French. However, results from self-paced reading indicated that subject-biased verbs were more difficult to process regardless of the construction, suggesting that the integration of implicit causality occurs at a later level of processing, such as in acceptability judgments and comprehension questions. Further acceptability judgment tasks suggested that implicit causality influences relative clause acceptability beyond word order and thematic roles. We propose linking the role of implicit causality with the function of a restrictive relative clause and introduce the Aboutness Hypothesis to explain relative clause processing: a relative clause is more acceptable and easier to understand when everything contributes to making the head its optimal aboutness topic.